Process and methodology for selecting cutting parameters for titanium

Abstract

A method of predicting the cutting speed for machining of titanium alloy comprising the steps of obtaining a first transfer function for a tool system, obtaining a second transfer function for a workpiece system, selecting from the first transfer function a first flexible mode, selecting from the second transfer function a second flexible mode, defining a natural frequency of the first flexible mode and the second flexible mode, calculating a tooth passing frequency using the defined natural frequency, accepting the calculated tooth passing frequency if the calculated tooth passing frequency differs from a second harmonic of a combined system formed of the tool system and the workpiece system and from at least one natural frequency corresponding to the tool system and the workpiece system, calculating a stable spindle speed, defining a cut depth using the calculated spindle speed.

What is claimed is:  
     
       1. A method of predicting the cutting speed for machining of titanium alloy comprising the steps of: 
       obtaining a first transfer function for a tool system;  
       obtaining a second transfer function for a workpiece system;  
       selecting from said first transfer function a first flexible mode;  
       selecting from said second transfer function a second flexible mode;  
       defining a natural frequency of said first flexible mode and said second flexible mode;  
       calculating a tooth passing frequency using said defined natural frequency;  
       accepting said calculated tooth passing frequency if said calculated tooth passing frequency differs from a second harmonic of a combined system formed of said tool system and said workpiece system and from at least one natural frequency corresponding to said tool system and said workpiece system;  
       calculating a stable spindle speed;  
       defining a cut depth using said calculated spindle speed.  
     
     
       2. The method of  claim 1  wherein said obtaining said first transfer function comprises the additional step of performing hammer impact testing in an X and Y plane. 
     
     
       3. The method of  claim 1  wherein said obtaining said second transfer function comprises the additional step of performing hammer impact testing in an X, a Y, and a Z plane. 
     
     
       4. The method of  claim 1  wherein said tooth passing frequency equals said natural frequency of said first flexible mode and said second flexible mode divided by (n+0.25) wherein n is an integer number. 
     
     
       5. The method of  claim 1  wherein said stable spindle speed equals ((said tooth passing frequency)*60/N) where N equals a number of teeth. 
     
     
       6. The method of  claim 1  wherein said cut depth equals 1/(2kN′R e [G] min ) wherein k is the specific cutting force for titanium, R e [G] min  is a minimum value of a real part of said first or said second transfer function, and N′ is an average number of teeth that are in a cut. 
     
     
       7. The method of  claim 1  wherein obtaining said second transfer function comprises the additional steps of: 
       creating a CAD model for said workpiece system;  
       performing finite element analysis to compute a frequency response function;  
       creating a CAM model of said workpiece system defining at least one process step to be performed on said workpiece system; and  
       simulating a removal of material in accordance with said at least one process step to compute an updated frequency response function and said second transfer function.  
     
     
       8. The method of  claim 1  wherein obtaining said first transfer function comprises the additional steps of: 
       creating a CAD model for said tool system;  
       performing finite element analysis to compute a frequency response function; and  
       generating said first transfer function from said frequency response function.  
     
     
       9. The method of  claim 1  comprising the additional steps of attaching actuators or sensors to said workpiece system and said tool system and adaptively altering a coupled dynamic system comprising said workpiece system and said tool system so as to transiently impact a plurality of modal resonances and responses.